It's possible that he may have a DPI settings change on his Windows machine that could be causing the issue. Windows has an option to change your DPI settings for text, which can sometimes change the rendering within Outlook clients. By default this is usually set at 96 DPI on Windows machines. Some users may change this to 120 DPI (or a custom number) for text for better readability. More information on Microsoft’s site here (http://windows.microsoft.com/en-us/windows-vista/make-the-text-on-your-screen-larger-or-smaller). If he has a different DPI setting than the default selection of 96 DPI on his Windows machine, you may see some rendering differences locally due to the change in settings. We use the default DPI setting of 96 on all of our Windows machines for previews on Litmus.

Also any zooming, plugins added to Outlook, or other settings changes made in Outlook or Windows can cause differences. More often than not I see customers emailing in with Outlook 2007 rendering problems and it ends up being the DPI change that causes the issue.

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